Abstract:Objective To analyze the clinical features and gene mutations types of 15 urelated probands with coagulation factor V(FV) deficiency, and explore the possible molecular pathogenesis.Methods FV activity (FV :C) and FV antigen(FV:Ag) weredetected by one-stage clotting and ELISA, respectively.All 25 exons of the F5 gene in the patients were amplified by PCR,and se-quenced diectly. Haplotype analysis was performed with different polymorphisms on FV.Protein modeling was applied to analyze thepotential molecular mechanisms.Results Of the 5 prokands with an F V:C greater than 10% , only l had minor bleeding symptoms. Ilnthe 10 proands with FV : C less than 10% ， seven showed various bleeding manifestations. A total of 12 gene mutations locus were de-tected from l5 probands (8 gene mutations locus were novel mutations , and 1 was pathogenic polymorphism).An in silico analysis pre-liminarily investigated the potential pathogenic mechanism of the mutation.Modleling analysis showed that all the six missense mutationswould lead to conformational alierations in the F V protein.Among them，two ( p.Ser1781Arg and p.Asp96His) would decrease hydro-gen bonds. Conclusion The level of FV in these probands with imherited F V deficiency were associated with mutations in the respec-tive F5 gene，and the FV levels strongly correlated with the probability of hemorrhage.